This invention is generally directed to photogenerating pigments such as titanyl phthalocyanines and processes for the preparation thereof, and more specifically, the present invention is directed to processes for obtaining titanyl phthalocyanine polymorphs or crystal forms, including the known Type IV, reference for example U.S. Pat. No. 4,898,799, the disclosure of which is totally incorporated herein by reference, Type X and layered photoconductive members comprised of the aforementioned titanyl phthalocyanine polymorphs, especially the Type IV and the Type X. In embodiments, the present invention is directed to a process for the preparation of titanyl phthalocyanines by the application of titanyl phthalocyanines to a cooled supporting substrate, like aluminum, and thereafter treating the substrate with a solvent, like an alcohol. In one embodiment, the present invention is directed to a process for the preparation of a high purity titanyl phthalocyanine, especially titanyl phthalocyanine Type IV, by applying titanyl phthalocyanine Type II to a substrate cooled to a temperature below 25.degree. C., and preferably from between about -10.degree. to about -30.degree. C.; permitting the substrate to attain room temperature, about 25.degree. C. and subsequently treating, for example, by dipping the substrate into an aliphatic alcohol with 1 to about 12 carbon atoms like methanol. Advantages associated with the processes of the present invention are the provision of a high purity titanyl phthalocyanine, especially Type IV, which purity ranges from about 95 to about 99.5 percent in embodiments, and wherein the titanyl phthalocyanine Type IV contains minimal, or substantially no Type If titanyl phthalocyanine; and superior photosensitivity for the titanyl phthalocyanine obtained, that is for example E.sub.1/2 =0.8 to 1.0 ergs/cm.sup.2 at .lambda.=800 nanometers as compared to a sensitivity of E.sub.1/2 =1.3 to 3.2 ergs/cm.sup.2 at .lambda.=800 nanometers for a number of prior art obtained titanyl phthalocyanines where, for example, the substrate temperature was retained above room temperature during the deposition. Layered imaging members with the aforementioned Type IV as a photogenerator, a charge transport, especially an aryl amine as illustrated herein, and a supporting substrate possess excellent photosensitivity. The titanyl phthalocyanines, especially the known polymorph IV and the X form, can be selected as organic photogenerator pigments in photoresponsive imaging members containing charge, especially hole transport layers such as known aryl amine hole transport molecules. The aforementioned photoresponsive imaging members can be negatively charged when the photogenerating layer is situated between the hole transport layer and the substrate, or positively charged when the hole transport layer is situated between the photogenerating layer and the supporting substrate. The layered photoconductive imaging members can be selected for a number of different known imaging and printing processes including, for example, electrophotographic imaging processes, especially xerographic imaging and printing processes wherein negatively charged or positively charged images are rendered visible with toner compositions of the appropriate charge. Generally, the imaging members are sensitive in the wavelength regions of from about 550 to about 850 nanometers, thus diode lasers can be selected as the light source. Titanyl phthalocyanines may also be selected as intense blue light stable colorants for use in coatings, such as paint, inks, and as near infrared absorbing pigments suitable for use as IR laser optical recording materials.
Titanyl phthalocyanines, including Type IV, as photogenerating pigments in layered photoconductive imaging members are known. The use of certain titanium phthalocyanine pigments as a photoconductive material for electrophotographic applications is known, reference for example British Patent Publication 1,152,655, the disclosure of which is totally incorporated herein by reference. Also, U.S. Pat. No. 3,825,422 illustrates the use of titanyl phthalocyanine as a photoconductive pigment in an electrophotographic process known as particle electrophoresis. Further, as mentioned in the textbook Phthalocyanine Compounds by Moser and Thomas, the disclosure of which is totally incorporated herein by reference, polymorphism or the ability to form distinct solid state forms is well known in phthalocyanines. For example, metal-free phthalocyanine is known to exist in at least 5 forms designated as alpha, beta, pi, X and tau. Copper phthalocyanine crystal forms known as alpha, beta, gamma, delta, epsilon and pi are also described. These different polymorphic forms are usually distinguishable on the basis of differences in the solid state properties of the materials which can be determined by measurements, such as Differential Scanning Calorimetry, Infrared Spectroscopy, Ultraviolet-Visible-Near Infrared spectroscopy and, especially, X-Ray Powder Diffraction techniques. There appears to be general agreement on the nomenclature used to designate specific polymorphs of commonly used pigments such as metal-free and copper phthalocyanine. However, this does not appear to be the situation with titanyl phthalocyanines as different nomenclature is selected in a number of instances. For example, reference is made to alpha, beta, A, B, C, y, and m forms of TiOPc (titanyl phthalocyanine) with different names being used for the same form in some situations. It is believed that five main crystal forms of TiOPc are known, that is Types I, II, III, X, and IV. In Japanese 62-256865 there is disclosed, for example, a process for the preparation of pure Type I involving the addition of titanium tetrachloride to a solution of phthalonitrile in an organic solvent which has been heated in advance to a temperature of from 160.degree. to 300.degree. C. In Japanese 62-256866, there is illustrated, for example, a method of preparing the aforementioned polymorph which involves the rapid heating of a mixture of phthalonitrile and titanium tetrachloride in an organic solvent at a temperature of from 100.degree. to 170.degree. C. over a time period which does not exceed one hour. In Japanese 62-256867, there is described, for example, a process for the preparation of pure Type II (B) titanyl phthalocyanine, which involves a similar method to the latter except that the time to heat the mixture at from 100.degree. to 170.degree. C., is maintained for at least two and one half hours. Types I and II, in the pure form obtained by the process of the above publications, apparently afforded layered photoresponsive imaging members with excellent electrophotographic characteristics.
In Mita EPO Patent Publication 314,100, there is illustrated the synthesis of TiOPc by, for example, the reaction of titanium alkoxides and diiminoisoindoline in quinoline or an alkylbenzene, and the subsequent conversion thereof to an alpha type pigment (Type II) by an acid pasting process, whereby the synthesized pigment is dissolved in concentrated sulfuric acid, and the resultant solution is poured onto ice to precipitate the alpha-form, which is filtered and washed with methylene chloride. This pigment, which was blended with varying amounts of metal free phthalocyanine, could be selected as the electric charge generating layer in layered photoresponsive imaging members with a high photosensitivity at, for example, 780 nanometers.
In Mitsubishi Laid Open Japanese Application 90-269776, laid open date Nov. 5, 1990, the disclosure of which is totally incorporated herein by reference, there is illustrated the preparation of titanyl phthalocyanines by the treatment of phthalocyanines, such as metal free, metal phthalocyanines, or their derivatives with solvents containing at least trifluoroacetic acid, or mixed solvents of trifluoroacetic acid and halogenated hydrocarbons such as methylene chloride. In Example I of this Japanese Laid Open Application the preparation of the C-form of TiOPc is described. Other forms obtained are described in Examples II and III.
Processes for the preparation of specific polymorphs of titanyl phthalocyanine, which require the use of a strong acid such as sulfuric acid, are known, and these processes, it is believed, are not easily scalable. One process as illustrated in Konica Japanese Laid Open on Jan. 20, 1989 as 64-17066 (U.S. Pat. No. 4,643,770 appears to be its equivalent), the disclosure of which is totally incorporated herein by reference, involves, for example, the reaction of titanium tetrachloride and phthalonitrile in 1-chloronaphthalene solvent to produce dichlorotitanium phthalocyanine which is then subjected to hydrolysis by ammonia water to enable the Type II polymorph. This phthalocyanine is preferably treated with an electron releasing solvent such as 2-ethoxyethanol, dioxane, N-methylpyrrolidone, followed by subjecting the alpha-titanyl phthalocyanine to milling at a temperature of from 50.degree. to 180.degree. C. In a second method described in the aforementioned Japanese Publication, there is disclosed the preparation of alpha type titanyl phthalocyanine with sulfuric acid. Another method for the preparation of Type IV titanyl phthalocyanine involves the addition of an aromatic hydrocarbon, such as chlorobenzene solvent to an aqueous suspension of Type II titanyl phthalocyanine prepared by the well known acid pasting process, and heating the resultant suspension to about 50.degree. C. as disclosed in Sanyo-Shikiso Japanese 63-20365, Laid Open in Jan. 28, 1988. In Japanese 171771/1986, Laid Open Aug. 2, 1986, there is disclosed the purification of metallophthalocyanine by treatment with N-methylpyrrolidone. Other prior art includes Japanese Publications 62-67044, 63-20354, 120564 and 228265; and U.S. Pat. Nos. 4,664,997 and 4,898,799.
To obtain a TiOPc-based photoreceptor having high sensitivity to near infrared light, it is believed necessary to control not only the purity and chemical structure of the pigment, as is generally the situation with organic photoconductors, but also to prepare the pigment in the correct crystal modification. The disclosed processes used to prepare specific crystal forms of TiOPc, such as Types I, II, III and IV, are either complicated and difficult to control as in the preparation of pure Types I and II pigments by careful control of the synthesis parameters by the processes described in Mitsubishi Japanese 62-25685,-6 and -7, or involve harsh treatment such as sand milling at high temperature, reference Konica U.S. Pat. No. 4,898,799; or dissolution of the pigment in a large volume of concentrated sulfuric acid, a solvent which is known to cause decomposition of metal phthalocyanines, reference Sanyo-Shikiso Japanese 63-20365, and Mita EPO 314,100.
Generally, layered photoresponsive imaging members are described in a number of U.S. patents, such as U.S. Pat. No. 4,265,900, the disclosure of which is totally incorporated herein by reference, wherein there is illustrated an imaging member comprised of a photogenerating layer, and an aryl amine hole transport layer. Examples of photogenerating layer components include trigonal selenium, metal phthalocyanines, vanadyl phthalocyanines, titanyl phthalocyanines, and metal free phthalocyanines.
In copending application U.S. Ser. No. 537,714 (D/90087), the disclosure of which is totally incorporated herein by reference, there are illustrated photoresponsive imaging members with photogenerating titanyl phthalocyanine layers prepared by vacuum deposition. It is indicated in this copending application that the imaging members comprised of the vacuum deposited titanyl phthalocyanines and aryl amine hole transporting compounds exhibit superior xerographic performance as low dark decay characteristics result and higher photosensitivity is generated, particularly in comparison to several prior art imaging members prepared by solution coating or spray coating, reference for example U.S. Pat. No. 4,429,029 mentioned hereinbefore.
In U.S. Pat. No. 5,153,313 (D/90244), the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of phthalocyanine composites which comprises adding a metal free phthalocyanine, a metal phthalocyanine, a metalloxy phthalocyanine or mixtures thereof to a solution of trifluoroacetic acid and a haloalkane; adding to the resulting mixture a titanyl phthalocyanine; adding the resulting solution to a mixture that will enable precipitation of said composite; and recovering the phthalocyanine composite precipitated product.
In U.S. Pat. No. 5,166,339 (D/90198), the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of titanyl phthalocyanine which comprises the reaction of titanium tetrapropoxide with diiminoisoindoline in N-methylpyrrolidone solvent to provide Type I, or .beta.-type titanyl phthalocyanine as determined by X-ray powder diffraction; dissolving the resulting titanyl phthalocyanine in a mixture of trifluoroacetic acid and methylene chloride; adding the resulting mixture to a stirred organic solvent, such as methanol, or to water; separating the resulting precipitate by, for example, vacuum filtration through a glass fiber paper in a Buchner funnel; and washing the titanyl phthalocyanine product.
Disclosed in U.S. Pat. No. 5,198,155 (D/91153) entitled "Titanium Phthalocyanines and Processes for the Preparation Thereof" with inventors James D. Mayo, Terry L. Bluhm, Cheng K. Hsiao, Trevor I. Martin and Ah-Mee Hor; and U.S. Pat. No. 5,182,382 (D/91154) entitled "Processes for Titanyl Phthalocyanines" with inventors James D. Mayo, James M. Duff, Trevor I. Martin, Terry L. Bluhm, Cheng K. Hsiao and Ah-Mee Hor, is a process for the preparation of titanyl phthalocyanine which comprises the treatment of titanyl phthalocyanine Type X with a halobenzene, the disclosures of which are totally incorporated herein by reference.
In U.S. Pat. No. 5,206,359 (D/91151), the disclosure of which is totally incorporated herein by reference, are processes for the preparation of titanyl phthalocyanine (TiOPc) polymorphs, which comprises, for example, the solubilization of a titanyl phthalocyanine Type I in a mixture of trifluoroacetic acid and methylene chloride, adding the resulting mixture slowly, for example dropwise, to an aliphatic alcohol with from 1 to about 12 carbon atoms, such as methanol, ethanol, propanol, butanol, and the like; precipitation of the desired titanyl phthalocyanine, such as Type X, separation by, for example, filtration, and optionally subjecting the product to washing, and thereafter treating the Type X titanyl phthalocyanine obtained with a halo, such as a chlorobenzene, to obtain Type IV titanyl phthalocyanine. The product can be identified by various known means including X-ray powder diffraction (XRPD).
The disclosures of all of the aforementioned publications, laid open applications, copending applications and patents are totally incorporated herein by reference.